BCMB 8020 Exam III Dr Schmidt s Lectures 100 points total April 5 2005 Name True False 1 2 point each 10 points total 1 With respect to a pure lipid membrane water crosses more efficiently than glucose ions cross more efficiently than glucose 2 The flow of water across a biological membrane is regulated by the opening and closing of water channels correlates with ion flow 3 Phosphorylation enhances the polarity of the modified side chain ionic interactions with glutamate and aspartate side chains 4 SCF type E3 ligases bind phosphorylated substrates are covalently modified with ubiquitin 5 Facilitated transport is typically highly specific with respect to cargo can involve the transport of molecules up their concentration gradients 6 Porins have a larger pore size than water channels are found on the inner membrane of Gram negative bacteria 7 Type I bacterial secretion is mechanistically similar to ER translocation involves the action of an ABC transporter 8 Regarding protein protein interaction domains PH domains bind phosphoserine residues SH2 domains bind phosphotyrosine residues 9 Regarding the use of radiolabeled azido ATP to probe enzyme function kinase substrates can be labeled using 32P ATP ATPases can be labeled using 32P ATP 10 Requirements for the application of FRET include fluorophores that emit at different wavelengths physical interaction between the fluorophores BCMB 8020 Exam III Name Multiple Choice 2 points each 20 points total 11 Based on the analogies presented in class where proteins are represented by plants and lipids by water a biological membrane is most like a A a dense forest with a few pools of water B a grassland with the occasional lake and river C a swamp with waterways bogs and small forested islands D a sea dotted with the occasional forested island 12 All of the following are key characteristics of plasma membranes except for A they are composed of lipids proteins and carbohydrates B they have similar ratios of lipids proteins and carbohydrates from organism to organism C the leaflets of the bilayer are asymmetric in composition D they are generally permeable to ions 13 Which of the following amino acids would you expect to find more likely than the others in a transmembrane segment A glutamate B leucine C lysine D serine 14 All of the following are hallmarks of eukaryotic secretory signal sequences except for A they have a tripartite composition B they interact with RNA C they are proteolytically cleaved at two or more sites D they target proteins to an ABC type transporter on the ER 15 P type transporters are phosphorylated on which of the following residues during their catalytic cycle A aspartate B cysteine C serine D tyrosine 16 Which of the following proteolytic mechanisms does not require a water nucleophile during the hydrolytic cycle A aspartate B cysteine C metallo D serine 2 BCMB 8020 Exam III Name 17 As a group ABC transporters exhibit which one of the following characteristics A they can transport a variety of substrates B they function only in the import of molecules C they are smaller than the average 30 kDa protein D they can be composed of four identical subunits 18 All of the following can occur during the transport of ions via channels except for A desolvation B transport of cargo down a concentration gradient C weak interactions with carbonyl atoms of helices that line the channel D generation of electrochemical gradients 19 The following are features of GPCR systems except for A they are used for transducing extracellular signals to the inside of the cell B they require a peptide ligand C they require a receptor that has multiple membrane spans D they are coupled to trimeric G proteins 20 All of the following contain a fatty acid component except for A sphingolipids B prostoglandins C GPI proteins D isoprenylated proteins Short Answer These can be answered using one or two keywords diagrams and or a short sentence 2 5 points each 36 points total 21 Draw the stick figure chemical structure of a 16 1 9 fatty acid 4 points 3 BCMB 8020 Exam III Name 22 Draw the chemical structure of an activated isoprene 3 points 23 What radiolabeled precursor would you use to specifically radiolabel the following 1 point each a all lipids b fatty acid based lipids to the exclusion of isoprene based lipids c glycerophospholipids and triacylglycerol to the exclusion of other lipids d sphingolipids 24 Historically why have phosphohistidine residues been difficult to detect 2 points 25 If a protein has a PH domain where is the likely subcellular localization of this protein 2 points 4 BCMB 8020 Exam III Name 26 Fatty acids have relatively low solubility in aqueous solutions What facilitates the circulation of fatty acids in the blood 2 points 27 Of the four proteolytic mechanisms which involve the formation of a covalent intermediate between the protease and its substrate 2 points 28 List the representative groups of lipid molecules that can be found covalently attached to proteins 5 points 29 As discussed in class list the four key events associated with signal transduction in whole cells 4 points 30 List the post translational modifications associated with regulation of IkB function and the resultant effect of these modifications 4 points 31 What is the purpose of a PDZ domain 2 points 32 What structural feature of chymotrypsin explains why it is inhibited by TPCK but not TLCK 2 points 5 BCMB 8020 Exam III Name Long Answer answer the following questions using several sentences and or diagrams 4 8 points each 34 points total 33 Describe the general events associated with NF B activation 6 points 34 Outline or diagram the general steps associated with SREBP mediated cholesterol homeostasis 8 points 6 BCMB 8020 Exam III Name 35 You are comparing the transport rates of ions across a synthetic membrane bilayer in the presence of two ionophores After measuring the transport rates at room temperature you chilled the same samples and reassessed transport rates At the lower temperature you notice that ionophore A no longer functions in ion transport while ionophore B remains functional albeit at a lower rate Provided that the temperature change does not alter the conformation of ionophore A or its ability to bind ions what reason do you posit as a simple explanation for your result Explain your reasoning 6 points 36 You have identified a periplasmic enzyme in E coli that is comprised of two subunits A and B that are encoded on separate genes You have